Using M_PI with C89 standard

Question

I\'m using C and trying to get access to the constant M_PI (3.14159...). I have imported the math.h header file, but the M_PI constant was still undefined. Through some sear

Answer 1

M_PI is not required by the C standard, it's just a common extension, so if you want to be standard you shouldn't rely on it. However, you can easily define your own #define for it, last time I checked it was a universal constant so there's not much space for confusion. :)